Side-by-side specifications of the Synology DS1621xs+ and DS1812+, from official datasheets. Differences are highlighted.
| DS1621xs+ | DS1812+ | |
| CPU | Intel Xeon D-1527 2.2/2.7 GHz | Dual Core 2.13 GHz |
| Cores / threads | 4 cores / 8 threads | 2 cores / 2 threads |
| RAM (base) | 8 GB DDR4 ECC SODIMM | 1 GB |
| RAM (max) | 32 GB | 3 GB |
| Drive bays | 6 | 8 |
| Expandable to | 16 total with 2× DX517 | 10 |
| M.2 slots | 2× M.2 2280 NVMe | 0 |
| Network | 2× 1GbE RJ-45, 1× 10GbE RJ-45 | 2x Gigabit |
| 10GbE | yes | no |
| Max raw capacity | 96 TB internal; 256 TB with 2× DX517 | 54 TB |
| Hot-swap | yes | yes |
| Form factor | Tower | Desktop |
| Released | 2020 | 2012 |
| Power consumption | — | 71.5 W / 28.6 W |
| DSM at launch | — | — |
Choose the DS1621xs+ if you want a much faster Intel Xeon CPU, far higher RAM ceiling, built-in 10GbE, and M.2 NVMe SSD cache support; it’s the clear performance/upgrade winner. Choose the DS1812+ only if you just need an older, basic 8-bay NAS with no 10GbE or M.2 and much lower headroom. The decisive tradeoff is modern speed and expansion on the 1621xs+ versus the older, simpler, cheaper 1812+.